FDA Approves Neonatal Fc Receptor Blocker Treatment for Individuals with Generalized Myasthenia Gravis

The Food and Drug Administration (FDA) has approved IMAAVY (nipocalimab; Johnson & Johnson, New Brunswick, NJ) for the treatment of individuals aged >12 years with generalized myasthenia gravis (gMG) who are anti-acetylcholine receptor (AChR) or anti-muscle-specific tyrosine kinase (MuSK) antibody positive. IMAAVY is a neonatal Fc receptor (FcRn) blocker administered via intravenous infusion which reduces immunoglobulin G levels. 

FDA approval was based on results from the phase 3, randomized, double-blind, placebo-controlled VIVACITY-MG study (NCT04951622). Participants enrolled in this study included adults aged ≥18 years diagnosed with gMG taking standard-of-care (SOC) therapy with Myasthenia Gravis Activities of Daily Living (MG-ADL) scores ≥6. Participants were assigned randomly 1:1 to receive either IMAAVY (30 mg/kg loading dose then 15 mg/kg every 2 weeks for maintenance dosing) or placebo infusions every 2 weeks added to SOC therapy in both groups for 24 weeks. 

In terms of results: 

• 41.3% of participants treated with IMAAVY achieved a ≥2-point improvement in MG-ADL scores for at least 4 consecutive weeks between weeks 10 and 22 compared with 29.2% in the placebo group (P=.04). 
• Improvements in MG-ADL scores were observed as early as day 8 in the IMAAVY-treated group. 
• The mean change in MG-ADL score from baseline to week 22 was –3.77 in the IMAAVY-treated group vs –2.24 reported in the placebo-treated group.

Reported adverse events were mild or moderate in the IMAAVY-treated group and were comparable to those reported in the placebo group. 

According to comments made by Samantha Masterson, President and CEO, Myasthenia Gravis Foundation, “We consistently hear from individuals living with myasthenia gravis who are hopeful for new treatment options that may help bring greater stability, independence and predictability to their lives. . .Today’s announcement provides another option which could help address the constant uncertainty and heavy physical and mental toll that MG symptom relapse presents to patients and their families.”